Japanese Unexamined Patent Application Publication No. 2003-108966 (PTL 1) discloses an antenna mounted in a mobile electronic device used in the RFID system. FIG. 1 is a sectional view of an antenna disclosed in PTL 1. In FIG. 1, an antenna coil 10 includes a coil body 11 and a core iron member 13. The coil body 11 is a spirally wound conductor disposed on one surface of an insulating film 12. The core iron member 13 is attached to another surface of the insulating film 12 in a layered manner.